6 Lacertidae. 



I have always objected to the recognition of zoogeographical primary 

 divisions except for restricted groups, on the ground that whilst they 

 apply to one group they do not, or may even be radically opposed, to 

 another, even of the same class or order. In the case of the present 

 family the Old World stands quite apart from the New, no doubt 

 because the extension to Northern Asia is comparatively recent, and 

 it is clear that there is no boundary at all to be drawn for the three 

 generally accepted great divisions in which they are represented. 

 There is no reason for regarding Arabia and the countries to the West 

 of the Eed Sea as Palsearctic rather than Ethiopian, whilst the character 

 of the Indo-Malay fauna is merely negative. That is why, in the above 

 list, I have given precedence to the divisions according to ordinary 

 physical geography. 



One striting fact is the nearly absolute concordance in the distribution 

 of the Lacertidae and the true Vipers (Viperinee), except for the absence 

 of the latter from various large islands in Europe (Ireland, Corsica, 

 Sardinia) as well as in Asia (Japan, Loo Choo, Formosa) and from 

 China. The northernmost species of the two groups, Lacerta vivipara 

 and Vipera berus, have an almost identical range. The Palsearctic- 

 Ethiopian distribution of the Lacertidte and Yiperinse is in striking 

 contrast with tha.t of the Anguidse, Scincidse, Coliibrinm, and Crota- 

 linse, the Palsearctic forms of which show Nearctic affinities, the more 

 pronounced as we proceed from West to East. It is noteworthy that 

 the two most generalised genera, Nucras among the Lacertids, Causus 

 among the Vipers, are now confined to Tropical and South Africa ; 

 Palseontology may some day enlighten us as to their northern origin, 

 which I regard as highly probable.* 



At present we are in the dark as to the immediate ancestors of the 

 Lacertidae ; we may, however, provisionally regard them on theoretical 

 grounds as derived from the Teiidae, now confined to America, but 

 which may have bad representatives in the Old World in Eocene times, 

 and which appear to be at least as old as the Cretaceous {Chamops, 

 Marsh, from the Laramie of Wyoming). These two families are 

 closely related, the former differing from the latter in the dermal 

 ossification over the skull and the ultra-pleurodont dentition, characters 

 expressive of a more advanced evolution. 



* 0/. G. A. Boulenger, Considerations sur les affinites et la dispersion 

 geographique des Laoertides. C. R. Ac. So. Paris, olxvi, 1918, p. 594. 



